Ultrafine particles have become desirable for use in many applications. As the average primary particle size of a material decreases to less than 1 micron a variety of confinement effects can occur that can change the properties of the material. For example, a property can be altered when the entity or mechanism responsible for that property is confined within a space smaller than some critical length associated with that entity or mechanism. As a result, ultrafine particles represent an opportunity for designing and developing a wide range of materials for structural, optical, electronic and chemical applications, such as coatings.
Various methods have been employed to make ultrafine particles. Among these are various vapor phase synthesis methods, such as flame pyrolysis, hot walled reactor, chemical vapor synthesis, and rapid quench plasma synthesis, among others. Unfortunately, such processes are often not commercially viable. First, in many cases, the use of solid precursors is not desirable in such processes because they vaporize too slowly for the desired chemical reactions to occur in the time before the vaporized stream cools. As a result, in many cases, if the use of a solid precursor is desired, it must be heated to a gaseous or liquid state before introduction into the vapor phase synthesis process. Second, the equipment utilized in such processes is often susceptible to fouling, which causes disruptions in the production process for cleaning of the equipment.
As a result, it would be desirable to provide a method for producing ultrafine particles that is suitable for use with a solid precursor and which results in a reduction or, in some cases, elimination of system fouling.